Frequency addressable beams of electromagnetic energy have been used in the past to provide beams of communication signals which are optimum for each user location. Such systems are sometimes referred to as a frequency scanning antenna system, wherein the location of each virtual beam that is formed is determined by the frequency of the user, with the user frequencies being spread out over an area in sight of the antenna. The beam may be thought of as being scanned over an area of the earth, as from east to west, for example, as the carrier frequency of the virtual beams thusly formed is increased.
In order to provide sufficient gain at each user site while reusing a given range of frequencies, the use of multiple scanning beams has been proposed to service a given area of the earth, as will be discussed below in more detail. However, in order to produce such multiple beams, it would be necessary to employ multiple antenna arrays and possibly more than one satellite to achieve the necessary coverage over the earth.
There is therefore a need in the art for a method and an apparatus for forming multiple frequency-addressable beams using a single antenna array deployed on a single satellite. The present invention satisfies this need, however, other objects and advantages of the present invention will become apparent from the detailed description thereof provided below.